Add Socket Firewall (sfw) to point 3

[karlhorky]

Since npq seems similar to Socket Firewall (sfw), I would suggest:

1. Splitting section 3 in two
2. Point 3.1 can stay as npq (or sfw could come first, not sure)
3. Point 3.2 can become sfw (or npq, if that's a better ordering)